Conventionally, dubbing of an MPEG (Moving Picture Experts Group) stream in which digital data such as motion video and audio are multiplexed (multiplexed coded data) is carried out while maintaining the form of the MPEG stream.
The reason is as follows. For example, when video data is coded by MPEG2 method while audio data is coded by MPEG1 method, the coded video data and the coded audio data are multiplexed as an MPEG stream for synchronization between these data. That is, the dubbing can be carried out at the highest efficiency when the coded video data and the coded audio data included in the MPEG stream are dubbed collectively as the MPEG stream. Another reason why the dubbing of the MPEG stream is conventionally carried out while maintaining the stream form is that there has been proposed no dubbing method other than such dubbing method.
FIG. 6 is a diagram for explaining the above-mentioned MPEG stream.
With reference to FIG. 6, video data coded by MPEG2 method (coded video data) Dvc and audio data coded by AC3 method (coded audio data) Dac are multiplexed as an MPEG stream Ds. Here, AC3 method is an audio coding method which is recommended in DVD (Digital Versatile Disk) video standards. Specifically, the MPEG stream Ds includes compressed video data Dvtc which is obtained by subjecting the coded video data Dvc to time-axis compression so that the data Dvc can be multiplexed with the coded audio data Dac, and compressed audio data Datc which is obtained by subjecting the coded audio data Dac to time-axis compression so that the data Dac can be multiplexed with the coded video data Dvc.
That is, the coded video data Dvc has such a data structure that it is divided in predetermined data units (GOP). For example, as shown in FIG. 6, the coded video data Dvc includes coded video data Dvc1 corresponding to 1st to 16th video frames F1 to F16 constituting a first GOP (Group of Pictures), and coded video data Dvc2 corresponding to 17th to 32nd video frames F17 to F32 constituting a second GOP. Further, as shown in FIG. 6, the compressed video data Dvtc includes time-axis-compressed data V1 to V3 corresponding to the first GOP, and time-axis-compressed data V4 to V6 corresponding to the second GOP.
The time-axis-compressed data V1 is obtained by performing time-axis compression on the forward part of the coded video data Dvc1 corresponding to the first GOP collectively, the time-axis-compressed data V2 is obtained by performing time-axis compression on the middle part of the coded video data Dvc1 collectively, and the time-axis-compressed data V3 is obtained by performing time-axis compression on the rearward part of the coded video data Dvc1 collectively. Further, the time-axis-compressed data V4 is obtained by performing time-axis compression on the forward part of the coded video data Dvc2 corresponding to the second GOP collectively, the time-axis-compressed data V5 is obtained by performing time-axis compression on the middle part of the coded video data Dvc2 collectively, and the time-axis-compressed data V6 is obtained by performing time-axis compression on the rearward part of the coded video data Dvc2 collectively.
Here, I data (intra-frame coded data) in the coded video data Dvc1 corresponding to the first GOP corresponds to frame F1, and P and B data (inter-frame coded data) corresponding to frames F2 to F16 are arranged subsequent to the I data corresponding to the frame F1. I data (intra-frame coded data) in the coded video data Dvc2 corresponding to the second GOP corresponds to frame F17, and P and B data (inter-frame coded data) corresponding to frames F18 to F32 are arranged subsequent to the I data corresponding to the frame F17.
Further, as shown in FIG. 6, the compressed audio data Datc includes time-axis-compressed data A1 to A3 corresponding to the first GOP, and time-axis-compressed data A4 to A6 corresponding to the second GOP.
The time-axis-compressed data A1, A2 and A3 are obtained by performing time-axis compression on parts of the coded audio data Dac, approximately corresponding to the time-axis-compressed data V1, V2 and V3 in the compressed video data Dvtc, respectively. Further, the time-axis-compressed data A4, A5 and A6 are obtained by performing time-axis compression on parts of the coded audio data Dac, approximately corresponding to the time-axis-compressed data V4, V5 and V6 in the compressed video data Dvtc, respectively.
FIG. 7 is a block diagram for explaining a dubbing process using a conventional signal processing apparatus, and illustrates a DVD player and a DVD recorder as a conventional signal processing apparatus.
Initially, a description will be given of a DVD player 201 as a conventional signal processing apparatus.
The DVD player 201 includes a driving means 10 for driving an optical disk 1 as a first recording medium on the basis of a control signal Cd1, and a reading means 2 for reading data Ds from the optical disk 1 on the basis of a control signal Cro. On the optical disk 1, coded video data and coded audio data, which are multiplexed, are recorded as an MPEG stream Ds. As the MPEG stream, there are a transport stream (TS) and a program stream (PS), and in either stream, coded video data and coded audio data are time-axis-compressed and then multiplexed so that the both data can be played back in synchronization with each other.
The DVD player 201 further includes a video decoding means 3 and an audio decoding means 5. The video decoding means 3 receives the MPEG stream Ds read from the optical disk 1, and decodes the coded video data which has been obtained by MPEG2 method and is included in the MPEG stream Ds to output a baseband (non-compressed) video signal Dvd. The audio decoding means 5 receives the MPEG stream Ds read from the optical disk 1, and decodes the coded audio data which has been obtained by AC3 method and is included in the MPEG stream Ds to output a baseband (non-compressed) PCM (Pulse-Code Modulation) audio signal Dad.
The DVD player 201 further includes a D/A converter 11 for D/A-converting the baseband video signal Dvd outputted from the video decoding means 3 to output an analog video signal Sv; a TV monitor 12 for performing image display on the basis of the analog video signal Sv; a D/A converter 13 for D/A-converting the baseband audio signal Dad outputted from the audio decoding means 5 to output an analog audio signal Sa; and a speaker 14 for outputting an audio output on the basis of the analog audio signal Sa.
The DVD player 201 further includes a user's operation unit 15; a control means 9 for outputting the control signals Cd1 and Cro to the driving means 10 and the reading means 2, respectively, as well as control signals (not shown) to the other means 3 and 5 and the D/A converters 11 and 13 on the basis of an operation signal Sop1 generated in the operation unit 15; and output terminals 201a and 201b for outputting the analog video signal Sv and the analog audio signal Sa to the outside of the player, respectively.
Next, a description will be given of a DVD recorder 202 as the conventional signal processing apparatus.
The DVD recorder 202 includes input terminals 202a and 202b for receiving the analog video signal Sv and the analog audio signal Sa, respectively; an A/D converter 21 for converting the analog video signal Sv into a baseband digital video signal Dv; and an A/D converter 22 for converting the analog audio signal Sa into a baseband digital audio signal Da.
The DVD recorder 202 further includes a video coding means 23 for coding the baseband video signal Dv Lo output coded video data Dvc; and an audio coding means 24 for coding the baseband audio signal Da to output coded audio data Dac.
The DVD recorder 202 further includes a driving means 27 for driving an optical disk 26 as a second recording medium on the basis of a control signal Cd2; and a recording means 25 for multiplexing the coded video data Dvc and the coded audio data Dac on the basis of a control signal Cre, and recording the multiplexed data as an MPEG stream Dw on the optical disk 26.
The DVD recorder 202 further includes a user's operation unit 29; and a control means 28 for outputting the control signals Crc and Cd2 to the driving means 27 and the recording means 25, respectively, as well as control signals (not shown) to the other means 23 and 24 and the A/D converters 21 and 22 on the basis of an operation signal Sop2 generated in the operation unit 29.
Next, a description will be given of the operation of the conventional signal processing apparatus
Initially, the operation of the DVD player 201 will be described.
In the DVD player 201, when a process of playing back the data recorded on the optical disk 1 as the first recording medium is selected by user's operation, the respective means of the DVD player 201 perform the data playback process on the basis of the control signals from the control means 9.
To be specific, initially, the optical disk 1 is driven by the driving means 10 that is controlled by the control signal Cd1, and the data Ds is read from the optical disk 1 by the reading means 2. The read data Ds is supplied from the reading means 2 to the video decoding means 3 and to the audio decoding means 5.
More specifically, the video decoding means 3 and the audio decoding means 5 are supplied with, as the data Ds, an MPEG stream including MPEG2-coded video data and AC3-coded audio data.
Then, the video decoding means 3 performs a video decoding process for extracting the MPEG2-coded video data from the MPEG stream Ds and decoding the data, whereby a baseband video signal Dvd is generated. This video signal Dvd is outputted to the D/A converter 11.
The D/A converter 11 performs a D/A conversion process for converting the video signal Dvd into an analog video signal Sv, and the analog video signal Sv is outputted to the TV monitor 12. The TV monitor 12 performs image display on the basis of the analog video signal Sv.
Further, simultaneously with the above-mentioned playback of the coded video data, the audio decoding means 5 performs an audio decoding process for extracting the AC3-coded audio data from the MPEG stream Ds and decoding the data, whereby a baseband PCM audio signal Dad is generated. This audio signal Dad is outputted to the D/A converter 13.
The D/A converter 13 performs a D/A conversion process for converting the audio signal Dad into an analog audio signal Sa, and the analog audio signal Sa is outputted to the speaker 14. The speaker 14 performs audio playback on the basis of the analog audio signal Sa.
Further, during the above-mentioned playback of the coded video data and the coded audio data, the analog video signal Sv and the analog audio signal Sa are outputted to the output terminals 201a and 201b of the DVD player 201, respectively.
Next, a description will be given of a dubbing process for recording the data recorded on the optical disk 1 as the first recording means, on the optical disk 26 as the second recording medium, by using the DVD player 201 and the DVD recorder 202.
In advance of performing the dubbing process, the output terminals 201a and 201b of the DVD player 201 are connected to the corresponding input terminals 202a and 202b of the DVD recorder 202, respectively.
In the DVD player 201, when an operation signal Sop1 is supplied from the user operation unit 15 to the control means 9, the control means 9 outputs control signals for controlling the respective parts. Further, in the DVD recorder 202, when an operation signal Sop2 is supplied from the user operation unit 29 to the control means 28, the control means 28 outputs control signals for controlling the respective parts.
Then, in the DVD player 201, the playback of the MPEG stream recorded on the optical disk 1 is carried out as described above, and the analog video signal Sv and the analog audio signal Sa obtained by the playback of the MPEG stream are outputted. On the other hand, in the DVD recorder 202, a recording process of subjecting the analog video signal Sv and the analog audio signal Sa outputted from the DVD player 201 to A/D conversion, coding and multiplexing, and recording data generated by the multiplexing is carried out.
To be specific, in the DVD player 201, the MPEG stream recorded on the optical disk 1 is played back, and thus the analog video signal Sv and the analog audio signal Sa obtained by the playback of the MPEG stream are outputted from the output terminals 201a and 201b of the DVD player 201 to the input terminals 202a and 202b of the DVD recorder 202, respectively.
In the DVD recorder 202, the analog video signal Sv inputted to the input terminal 202a is converted to a digital video signal Dv by the A/D converter 21, and supplied to the video coding means 23. On the other hand, the analog audio signal Sa inputted to the input terminal 202b is converted to a digital audio signal Da by the A/D converter 22, and supplied to the audio coding means 24.
In the video coding means 23, coded video data Dvc is generated by coding the digital video signal Dv, and in the audio coding means 24, coded audio data Dac is generated by coding the digital audio signal Da, and then the coded video data Dvc and the coded audio data Dac are supplied to the recording means 25.
The coded video data Dvc and the coded audio data Dac are multiplexed and recorded on the optical disk 26 by the recording means 25.
In this way, the dubbing process, i.e., recording of the MPEG stream recorded on the optical disk 1 as the first recording medium, on the optical disk 26 as the second recording medium, is carried out.
By the way, in recent years, portable recording mediums such as semiconductor memories or the like are becoming widespread, and there may be cases where digital data such as motion video and audio are dubbed on such portable recording mediums.
In a dubbing process to the portable recording mediums such as semiconductor memories or the like, it is sometimes required that not the whole of the video data and audio data multiplexed as the MPEG stream but a part of the video data and audio data or only one of the video data or the audio data is selectively recorded.
In this case, however, by the conventional technique of dubbing the MPEG stream while maintaining the stream form, it is difficult to appropriately record only a part of the video data and audio data multiplexed as the MPEG stream or either the video data or the audio data.